[ubuntu] Choosing updates

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I'm a bit afraid of breaking my machine because I've heard some people have had that problem after updating. How safe is it to just let update manager install all available updates? I currently have 300+ updates waiting and I've just been going through them and installing the ones that I know what they do. Some of them, like one of the linux kernal updates say to install a different one instead (linux-generic-pae-meta-package versus linux-generic-pae(new install)) and others are updates for applications I don't have (bunch of updates for Evolution; I'm using Thunderbird).
(Hardware)